Propellers for aeroplanes and the like



Aug. 23, 1932. L, STIPA 1,873,505

PROPELLERS FOR AEROPLANES AND THE LIKE Filed Aug. 26, 1931 2 Sheets-Sheet l l'l'g: 1.

lvva/vraz .Lu/a/ S-r/PA A T70ENE Aug. 23, 1932. L. STIPA 1,873,505

PROPELLERS FOR AEROPLANES AND THE LIKE' Filed Aug. 26 1951 2 Sheets-Sheet 2 li'gr 10.

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A T TOE/VEKS Patented Aug. 23, 1932 PATENT OFFICE L'UIGI strum, OF ROME, ITALY PROIPELLEBS FOR.AEROPLAN ES AND THE LIKE Application filed August 26, 1931, Serial No. 559,417, and in Italy September 1, 1930.

The present invention has reference to improvements in the mounting of screws for propelling aeroplanes, dirigibles, submarines, and generally aerial and aquatic vehicles of all kinds.

More particularly the invention has reference to propellers of the tubed type, viz; those which are designedto work inside and in conjunction with a tube, or which may be placed in front or at the rear of a tube, so that the current of the fluid sucked or ejected by the propeller passes through said tube.

The invention has for its object to increase as much as possible the efliciency of propellers ,thus mounted, and also to utilize the effect of the reaction due to the flow of fluid leaving at the rear end of the tube, also in the transformation of the dynamical into static'pressure in the diverging part of the tube. This" reaction has the effect of increasing the pro pelling action of the screw.

The results above mentioned are obtained by shaping the internal longitudinal section of the tube in such a manner, that when the propeller is placed either in front or inside the tube, the shape of the conduit formingthe passage for the flow of the fluid coincides with the shape that the wake would assume if the propeller was working freely immersed into the same fluid, and also that the tube or conduit be made of such a length as to comprise a conical converging part and a conical diverging part, suitably connected in correspondence with the most restricted section of the said wake, so that the inside of the tube has the shape of a Venturi tube. This arrangement above said may be improved so as to decrease the resistance to advancement and to increase the carrying capacity.

Said improvement is obtained by providing in correspondence to the upper fore part of the fuselage a number of openings leading to canals which in their turn open inside the Venturi tube in proximity of its most restricted section, at which point there is a maximum depression causing a strong inflow of air. If the openings are disposed in such way so that the air flows inward from the front, an increased impulse is obtained, if on the other hand the air flow comes from upwards an increase of the lifting power is obtained. It is also clear that by suitablyarranging a con venient number of openings, both the above said effects may be obtained in the same aircraft, viz; both the decrease in the resistance tothe flight and the increase in the lifting power.

In addition, the efficiency of the apparatus can be further increased by shaping the fluid vein so as to ensure the best possible adhesion 6 of it on the walls of the tube or a more rapid parting of the propellers wake, as will better be explained in the following description.

In the accompanying drawings are shown schematicall various embodiments of the invention, which are given by way of example.

Figs. 1, 2, 3 and 4 are respectively a view in front elevation, a view in side elevation,

a View of a diametrical longitudinal vertical section, and .a plan view of a monoplane driven by one propeller only, according to the present invention.

Figs. 5 and 6 are views in front elevation respectively of a monoplane and a biplane both fitted with two propellers, according to the present invention.

Figs. 7 and 8 show two vertical longitudinal sections of the fuselage so shaped as to lessen the resistance to advancement and to increase the lifting power respectively.

Figs. 9, 10, 11, '12 and 13 show other modi-' fications according to the invention.

In Figs. 1, 4, 5 and 6 the wing surface is shown complete only on one side of the aeroplane, and in the other figures it has been 35 omitted entirely.

As it may be seen from the drawings. the tube 1 has its inside outline shaped as a Venturi tube, which follows the contour of the wake 2-3 of the propeller, the restricted section corresponding both for size and position to the more restricted section of the free wake of the propeller 4 to which the tube is applied.

Externally, the longitudinal profile of tube 1 corresponds to the a; wing profile, and the tube is connected sideways with a wing and corresponds to the profile of a Wing more or less thick, according to whether the pilot is to be placed between the internal and external part of the tube, or not, so as to obtain a structure allowing of the utmost penetration and possessing the utmost lifting power.

The propeller 4 may be placed at the entrance side of the tube in the position shown, or may be laced also inside of it in the position 4, or in any intermediate posit on.

The motor 3 may be placed immediately behind the propeller, as shown 1n the drawings, or it may be placed in the position marked 9' inside the tube, in which case a suitable transmission is to be provided to transmit the movement to the pro eller 4.

The aircraft may e either a monoplane or a biplane, and in either of said cases may be provided with two or more propellers, each of which applied to the respective tube. The arrangement of the elevators and of the rudders may either be internal or' external to the tube, or partly internal and partly external and may also be located at the end or on the inside, or else at the back, supported by suitable holders.

According to the arrangement adopted, their area may be varied so as to ensure their efficiency. v

According to the modifications shown in Figs. 7 and 8, the fuselage carries within it a tube for the rear part 2 ofthe wake, the same as a Venturi tube, provided with an opening for the front part of the wake havin approximately the same diameter as that o the propeller 4, and a number of openings 5 arranged round the first opening in the fore-part of the fuselage.

From the openings 5, the canals 6 are provided leading in proximity of the more restricted section of the Venturi tube. The fluid threads of the wake 2-3 assume approximately the course shown in the drawm I he openings forming the crown 5 may also be substituted by a single annular opening concentrical to opening 3, thus forming a curved nozzle, which also reaches in proximity of the restricted section of tube 2. In this case radial ribs are provided to connect the nozzle core with the fore part of the opening of the tube.

In order to increase the lifting power (Flg. 8) openings 8 are provided so that the air may be sucked from the upper part. The

canals 7 which communicate with said openings, lead, also, as in the previous case, in proximity of the restricted section of tube 2. It will be understood that the invention may be carried out in any manner with the most convenient means, and various modifications can be introduced therein without departing from the principle of the invention. For lnstance, in addition to the body of the fuselage, further openings for'the purpose above described may be provided also in the fore part of the wing.

Similarly, as the longitudinal profile of the propellers wake varies according to the s eed of the propeller and also with the trave ling speed of the aircraft, an additional device may be (provided, which may be automatic or han varying the inner longitudinal profile of the Venturi tube when varying the speed of the aircraft or the number of revolutions of the propeller, said device being shown in Figs. 9, 10, 11, 12 and 13.

It will thus be possible to provide, on the longitudinal inner wall of the tube, an adjustable or fixed device as shown in Figs. 9 and 10, which will permit to straighten, with respect to the longitudinal axis of the tube, the streamlines in the wake of the propeller, which have a whirling movement imparted to th'em'by the propeller. Said device may consist in a number of peripherical grooves (Fig. 10), and serves also to oppose the action of the motor torque acting on the aircraft, as it produces a momentum in the opposite direction to the momentum of the said motor torque.

The straightening of the propellers wake may also be accomplished by means of a second propeller mounted loose behind the driving propeller, as shown in Fig. 11.

Further, in the restricted section of the Venturi tube, or in proximity of said section, sleeves or like ap liances may be provided, for producing a etter adherence or a more rapid parting of the wake of the ropeller from the inside walls of the fuse age, as shown in Figs. 12 and 13.

I claim:

1. In a device of the character described, a propeller, means for driving said propeller, a tube having a Venturi-shaped interior surface and a wing-shaped surface connected with said tube, at least a part of said tube being situated behind said propeller, the exterior surfaces of said tube forming a continuation of said wing surface, the o ening of said tube nearest to said propeller aving a diameter substantially equal to the diameter of said propeller, the cross-sections of said tube being proportional to and slightly larger than the corresponding sections of the wake roduced by said propeller.

2. n a device of-the character described, a propeller, means for driving said propeller, a tube having a Venturi-shaped interior surface and a wing-shaped surface connected with said tube, at least a part of said tube being situated behind said propeller, the exterior surfaces of said tube forming a con tinuation of said wing surface, the opening of said tube nearest to said propeller having a diameter substantially equal to the diameter of said propeller, said tube having channels leading to the narrowest portion of the interior of said tube and provided with openings situated around the first-mentioned opening, the cross-sections of said tube being controlled, for the purpose of proportional to and slightly lar er than the corresponding sections of the Wa lie produced by said propeller.

3. In a device of the character described,

' a propeller, means for driving said propeller,

a tube having a venturi-shaped interior surface, and a wing-shaped surface connected with said tube, at least a part of said tube being situated behind said propeller, the eX-, terior surfaces of said tube forming a continuation of said wing surface, the opening of said tube nearest to said propeller having a diameter substantially equal to the diameter of said propeller, said tube having an annular channel leading to the narrowest portion of the interior of said tube and provided with an opening situated around the first-mentioned opening, the cross-sections of said tube being proportional to and slightly larger than the corresponding sections of the wake produced by said propeller.

4. In a device of the character described, a propeller, means for driving said propeller, a tube having a venturi-shaped interior surface and a wing-shaped surface connected with said tube, at least a part of said tube being situated behind said propeller, the exterior surfaces of said tube forming a continuation of said wing surface, the opening of said tube nearest to said propeller having a diameter substantially equal to the diameter of said propeller, the upper part of said tube having channels leading to the narrowest portion of the interior of said tube, the cross-sections of said tube being proportional to and slightly larger than the corresponding sections of the wake produced by said propeller.

5. In a device of the character described, a propeller, means for driving said propeller, a tube having a venturi-shaped interior surface provided with a plurality of longitudinal and peripheric grooves, and a wingshaped surface connected with said tube, at

least a part of said tube being situated behind said propeller, the exterior surfaces of said tube forming a continuation of said wing surface, the opening of said tube nearest to said propeller having a diameter substantially equal to the diameter of said propeller, the cross-sections of said tube being proportional to and slightly larger than the corresponding sections of the wake produced by said propeller.

6. In a device of the character described, a shaft, a propeller rigidly connected with said shaft, means for driving said shaft, a second propeller loosely mounted on said shaft behind the first-mentioned propeller, a tube having a venturi-shaped interior surface, and a wing-shaped surface connected with said tube, at least a part of said tube being situated behind the first-mentioned propeller, the exterior surfaces of said tube forming a continuation of said wing surface,

LUIGI STIPA. 

